In a typical paper or pulp treating machine, the web advances over a series of rolls arranged to form a zig-zag web path. In the presently preferred lacing system for such machines, a pair of cables are supported in parallelism with the web path at opposite ends of the rolls by pulleys in adjacent coaxial relation with the ends of the rolls. One cable is a drive cable for the rolls and is supported on pulleys rotatably connected with associated rolls by override clutches. The drive cable is driven by, e.g., a motor which can accelerate the rolls from rest to operating speed during a lacing operation. The pulleys at the other end of the rolls are free-wheeling and support a second cable which has the function of supporting one end of a bar extending transversely of the web path from one cable to the other. The second cable is driven by the drive cable by a cross shaft mounting sheaves in contact with both cables. The bar has the function of leading the other elements of the lacing equipment and the advancing tail of the web through the machine. Before initiation of a lacing operation, the unloaded free-wheeling rolls would be at rest. It is necessary to connect a tail of the web with the lacing apparatus and energize the drive cable to accelerate the rolls to operating speed while lacing the web through the machine.
Because of the web path widths on the order of 12 feet or more, the bar must be constructed strongly enough to resist bending under centrifugal force as it travels around the roll. Bars in use commonly weigh 75 pounds.
Occasionally, one cable is caused to lag the other to place the bar on a bias with respect to its normally perpendicular alignment to the web path. This can lead to disastrous results as the bar attempts to go around the rolls. There is the hazard of the cables jumping the pulleys and a safety hazard to personnel in the vicinity of rapidly moving unguided parts. Hence, some of the more obvious disadvantages of the principal lacing apparatus in use in view of the present invention relate to operating safety, mechanical complication, loss of time to accelerate unloaded rolls to operating speed, speed synchronization of the two cables, lost time in maintaining proper adjustments, excessive weight of parts, and an increasing difficulty to cope with increased web and roll speeds.
In addition to overcoming the above-named disadvantages, objects of the invention are: to provide lacing apparatus for web handling machinery which enables clamping of the web without the necessity for forming a web tail by manual tearing; to provide threading apparatus which avoids the necessity for breaking or severing the web to provide a tail; to provide apparatus of lower cost than that now in general use; to provide threading apparatus which may advance around rolls defining the web path without being centrifugally urged out of the path; and to provide the lacing mechanism which can be driven from at least one of the rolls independently of the other conventional roll driving cable.